This invention relates to wound dressings and particularly but not exclusively to such dressings as are useful in the treatment of heavily exuding wounds and in first aid, especially industrial first aid.
The following seven requirements have been specified for an ideal wound dressing, namely that it should:
1. Remove excess exudate away from the wound surface PA1 2. Maintain high humidity at the wound/dressing interface PA1 3. Provide thermal insulation PA1 4. Allow gaseous exchange, and the passage of water vapour PA1 5. Not shed fibres nor leach out toxic substances PA1 6. Be impermeable to microorganisms PA1 7. Not cause trauma during removal from the wound Turner T. D., in Proceedings of a Symposium on Wound Healing (Sundell B.ed) pp 75-84 (1978) ! PA1 "A non-reticulated polyurethane foam material, the foam cells adjacent at least one surface of which are irreversibly partially collapsed relative to foam cells remote from said surfaces and which surface is absorbent to aqueous based liquids"; PA1 a) Polyether polyol rich in ethylene oxide (Polyol 1) PA1 b) Branched ethylene oxide modified polyether polyol (Polyol 2) PA1 c) Toluene diisocyanate (T80/20) PA1 d) Dimethyl ethanolamine (DMEA) PA1 e) Triethylene diamine (TEDA) PA1 f) Polysiloxane--polyoxyalkylene block copolymer (cell stabiliser) PA1 g) Water or alternative blowing agent
All but the first of these requirements are fully met by a foam of the type described in the Specification of our UK Patent No 1 417 962, Claim 1 of which is in the following terms:
or in the Specification of the Patent of Addition thereto which is directed to a similar, but reticulated, foam material. Such foams are commercially available, being sold under the name LYOFOAM (Registered Trade Mark) and they have achieved widespread acceptance in the treatment of moderately exuding wounds. However, they may not have sufficient absorbency to absorb all the exudate from heavily exuding wounds.
Accordingly there is still a need for a dressing with sufficient absorbency for use on heavily exuding wounds, and it is an aim of the present invention to provide such a dressing.
Various methods investigated by the Applicants to achieve a higher absorbency foam dressing were found to be attended by certain drawbacks. The incorporation of a surfactant during manufacture of the foam did achieve slightly increased Absorbency but posed problems with regard to the presence of free surfactant in the final product and in achieving adherence of a backing layer which is often necessary to exclude bacterial infection.
The incorporation of an alginate during manufacture of the foam was attended by degradation of the alginate (a polysaccharide) and consequent impairment of its absorbent and haemostatic properties and also deterioration in the appearance of the foam.